Method and apparatus for detecting mispick in loom

ABSTRACT

A method for detecting the so-called &#39;&#39;&#39;&#39;mispick&#39;&#39;&#39;&#39; in a loom and a weft detector for a loom adapted to determine whether a required length of weft is properly picked into a warp shed, by detecting a temporary rise in the warp tension caused by the weft upon beating. The weft detector comprises a warp tension sensor for detecting the temporary rise during beating and a control circuit connected to the warp tension sensor for stopping the operation of the loom upon detection of the mispick, that is, in the absence of the temporary raise in the warp tension.

United States Patent Gotoh 1 July 25, 1972 54 METHOD AND APPARATUS FOR 3,390,708 7/1968 Scherillo ..139/370 DETECTING MISPICK IN LOOM Primary Examiner-Henry S. Jaudon [72] Inventor. Mlyuki Gotoh, Tokyo, Japan Atmmey McCanhy Depaoli & O'Brien [73] Assignee: Nissan Motor Company, Limited,

Yokohama, Japan [57] ABSTRACT Filed: 1970 A method for detecting the so-calied mispick" in a loom and 21 A L N J 98 428 a weft detector for a loom adapted to determine whether a l 1 pp 0 required length of weft is properly picked into a warp shed, by detecting a temporary rise in the warp tension caused by the 52 us. Cl ..139/370, 139/336 ft upon beating The fl detector comprises a warp [51] f -D03d51/13,D03d 51/34 sion sensor for detecting the temporary rise during beating [58] Field of Search ..l39/336, 337, 339, 370 and a control circuit connected to the warp tension Sensor for stopping the operation of the loom upon detection of the [56] References cued mispick, that is, in the absence of the temporary raise in the UNITED STATES PATENTS 7/1966 Suaty et al. ..i39/370 warp tension.

8 Claims, 3 Drawing Figures Patented July 25, 1972 2 Sheets -Sheet 1 Patented July 25, 1972 2 Sheets-Sheet 2 O@ O y i mOZ . 6 1m Q20 mm m sq METHOD AND APPARATUS FOR DETECTING MISPICK lN LOOM This invention relates to a method for detecting the socalled mispick in a loom and a weft detector adapted for a loom adapted to determine by detecting a temporary rise in the warp tension whether a required length of weft is properly inserted into a warp shed.

In an ordinary shuttleless loom, a feeler for feeling electrically a travelling end portion of a weft is employed to detect the mispick. A representative of the feeler is adapted to detect the current flowing between its two electrodes disposed at a distance from the selvage when the end portion of the weft containing water reaches and touches the electrodes after travel. Therefore, in case where the end portion of the weft is allowed to travel as far as the edge or selvage of a textile fabric but does not come into contact with the feeler, there will arise a problem in that the feeler provides a signal indicating the existence of the mispick, although a fabric product having such improperly inserted weft yarns is of acceptable quality. Furthermore, the feeler tends to become ineffective in sensing the weft end after a yarn waste has sticked thereto. Still furthermore, the operation characteristics of the feeler are affected by the resistivity variation in water contained in the weft. Consequently, the feeler is not suitable for a loom wearing a hydrophobic fabric such as of polyester.

This invention is based on the observation that when a textile fabric of usual weft density is produced the warp tension is temporarily and cyclically increased due to a beating pressure exerted on a dent. On the contrary, the warp tension remains substantially unchanged during beating where a required length of weft is not properly picked into a warp shed. According to the teachings of the invention there is provided a warp tension sensor which serves to detect the temporary rise in the warp tension so as to determine whether a required length of weft is properly picked into the warp shed.

It is therefore an object of this invention to provide a novel method and apparatus used in a loom for determining by detecting a temporary rise in the warp tension whether a required length of weft is properly picked into a warp shed.

It is another object of this invention to provide a novel weft detector having a warp tension sensor which serves to detect a temporary rise in the tension of a warp array during beating.

It is a further object of this invention to provide a novel weft detector which is adapted to stop the operation of a loom upon detection of a mispick.

In the drawings:

FIG. 1 is a schematic view of a loom incorporating the present weft detector;

FIG. 2 is an enlarged perspective view of a warp tension sensor used in the present mispick detector; and

FIG. 3 is a block diagram of a control circuit for the present weft detector.

Referring now to FIG. 1 which schematically illustrates a loom having the present weft detector, reference numeral designates a warp beam from which a warp array 11 is let off to a heald 12 by way of a back rest roller 13. As is well known, the heald 12 serves to have an over and under shed portions of the parallel warp arrays l4, 15 extending in their tensioned state so as to form a shed l6 therebetween. Weft inserting or picking means is provided for picking a required length of weft into the warp shed 16 and may, for example, comprise a shuttle or an injection nozzle (not shown). The loom also includes a reed 17 which is adapted to be operated to beat the length of weft to the cloth-fell 18 immediately after the length of weft has been picked into the warp shed 16, whereby fabric 19 is successively formed. The fabric 19 thus formed is supplied through a friction roller 20 to a cloth roller 21 where it is wound thereon.

According to the teachings of the invention there is provided a warp tension sensor 22 between the back rest roller 13 and the heald 12 on the side of the warp array 11 opposite to the weft inserting or picking means. As is best shown in FIG. 2, the warp tension sensor 22 comprises a pair of parallel-spaced guide members 23 and 24 extending on an edge portion 25 of the warp array 11 transversely to the same and a sensing element 26 positioned relative to and in contact with the guide members 23 and 24 to bias the edge portion 25 of the warp array 11 upwards. The relative position of the guide members 23 and 24 and the sensing element acts to convert the horizontal tension variation into a vertical pressure. It is preferable that the edge portion 25 is approximately I percent as wide as the entire warp array 11. The guide members 23 and 24 are 10 journaled to a bracket 27 by suitable means (not shown), the

bracket 27 being adjustably mounted on a stationary rod 28 for accommodation to different breadths of cloth. A support arm 29 is also secured to the bracket 27 by means of a screw 30 and has a flat surface (not shown) at one end thereof which is in parallel with the plane of the warp array 11. Mounted on the surface of the support arm 29 is an elongated sensing member 31 of piezoelectric type, on both sides of which are positioned two elongated resilient members 32 and 33. A semi-cylindrical member 34 is disposed on the sensing member 31 and the resilient members 32 and 33 so that a downward force whose magnitude is proportional to the warp tension is applied through the semi-cylindrical member 34 to the piezo-sensing member 31. The sensing member 31 has attached thereto lead wires (not shown) which are connected to a control circuit, which will be described hereinafter. The sensing member 31 of piezoelectric type may be replaced by any other suitable sensing means such as of magnetic type, if it detects the tension variation of the warp array.

FIG. 3 is a block diagram of the control circuit adapted to stop the operation of the loom upon detection of a mispick. The sensing member 31 of the warp tension sensor 22 is shown as connected first pre-amplifier 35 whose output is connected to one of the two input terminals of an AND circuit 36. A first pulse generator 37 is connected to a second pre-amplifier 38 which in turn is connected to the other input of the AND circuit 36. The first pulse generator 37 may be of any desired conventional construction and serves to generate a single pulse at beating. The AND" circuit 36 has its output connected to a one-shot multivibrator 39 which in turn is connected to one of the two inputs of a NOR" circuit 40.

A second pulse generator 41 is provided which serves to generate a single pulse in a predetermined time interval after the beating has taken place. It is to be noted that the predetermined time is shorter than the period of time that the one-shot multivibrator 39 remains in its quasi-stable state. The second pulse generator 41 is connected to a third pro-amplifier 42 having its output connected to a NOT" circuit 43 which in turn is connected to the other input of the NOR" circuit 40. The NOR" circuit 40 is connected to a memory circuit 44 whose output is connected to a power amplifier 45 which in turn is connected to a relay 46. The relay 46 when energized serves to actuate a switch 47 to open the power supply line 48 leading to the loom.

The arrangement thus far described is operated as follows:

When a required length of weft properly picked into a warp shed is beaten, the tension of a warp array is temporarily increased, so that the sensing member 31 of the warp tension sensor 22 provides an electric signal 50 as shown in FIG. 3. The electric signal 50 is amplified by the first pre-amplifier 35 to provide a rectangular pulse, as indicated at 51, which pulse is supplied to the AND" circuit 36. If a required length of weft is not inserted into the warp shed, the warp tension remains substantially unchanged during beating, so that the output of the pre-amplifier continues to be in the 0 state as represented by 52. The first pulse generator 37 provides an electric signal 53 during beating, which signal is amplified by the second pre-amplifier 38 to provide a rectangular pulse 54. If the two inputs are in the l state, that is, a length of weft is properly inserted, the AND circuit 36 provides a true (1) output 55 which in turn is supplied to the one-shot multivibrator 39 to provide a rectangular pulse 56 having an increased pulse width. If the length of weft is not properly inserted, the output of the AND circuit 36 remains in the 0 state during beating. The rectangular pulse 56 from the one-shot multivibrator 39 is supplied to one of the two inputs of the NOR" circuit 40. The second pulse generator 41 provides an electric signal 57 in a predetermined time interval after the beating has taken place. The electric signal 57 is amplified by the third pre-amplifier 42 to provide a rectangular pulse 58 which is supplied to the NOT" circuit 43. The NOT" circuit 43 provides an output signal, as indicated at 59, which signal is supplied to the other input of the NOR" circuit 40. If the two inputs are in the state, the NOR" circuit 40 provides a true 1) output 60 which in turn is supplied to the following memory circuit 44 to provide an output signal as indicated at 61. The output signal 61 is amplified by the power amplifier 45 so asto energizethe relay 46. The relay 46, when energized, actuates the switch 47 to open the power supply line 48 so as to stop the operation of the loom. Thus, it is to be understood that the switch 47 is actuated to open the power supply line only 48 only when a required length of weft not having been properly inserted into the warp shed is beaten.

Thus, the weft detector of this invention is advantageous in that it can be used in looms not only of shuttle type but of shuttleless type. If the cyclic levels of the warp tension are previously known, in addition, the weft detector can also be used in a loom provided with Dobby.

What is claimed is: g

l. A method for determining whether a required length of weft is properly picked into a warp shed, comprising detecting a temporary rise in the warp tension caused by the weft upon beating.

2. A weft detector adapted for use in a loom adapted to determine whether a required length of weft is properly picked into a warp shed, comprising a warp tension sensor for detecting a temporary rise in the tension of a warp array during beating, and means connected to said warp tension sensor for stopping the operation of said loom in the absence of said temporary rise in the warp tension.

3. A weft detector according to claim 2, in which said warp tension sensor comprises two parallel-spaced guide members extending on a portion of said warp array transversely to the same and a sensing element positioned relative to and in contact said guide members to bias said portion of the warp array.

4. A weft detector according to claim 3, in which said sensing element comprises a support arm having a flat surface which is in parallel with the plane of said warp array, a sensing member affixed to said surface of the support arm two elongated resilient members positioned on both sides of said sensing member, and a semi-cylindrical member disposed on said sensing member and said resilient members.

5. A weft detector according to claim 4, in which said sensing member is of pieioelectric type.

6. A weft detector according to claim 4, in which said sensing member is of magnetic type.

7. A weft detector according to claim 4, in which said support arm is secured to a bracket which is adjustably mounted on a stationary rod for accommodation to different breadths' of cloth.

8. A weft detector according to claim 2, in which said means comprises a first pre-amplifier connected to said warp tension sensor for amplifying an electric signal corresponding to said temporary change in the warp tension, a first pulse generator for generating a single pulse at beating, a second pre-amplifier connected to said first pulse generator for amplifying said pulse signal, an AND circuit having its two inputs connected to the outputs of said first and second pre-amplifiers, a oneshot multivibrator connected to the output of said AND circuit, a second pulse generator for generating a single pulse in a predetermined time interval after the beating has taken place, a third pre-amplifier connected to said second pulse generator for amplifying said pulse signal, a NOT circuit connected to the output of said third pre-amplifier, a NOR circuit having its two inputs connected to the outputs of said one-shot multivibrator and said NOT circuit, a memory circuit connected to the outgut of said NQR circuit, a power amplifier connected to t e output of said memory circuit, a relay connected to the output of said power amplifier, and a switch adapted to be actuated by said relay to open the power supply line leading to said loom in the absence of said temporary change in the warp tension. 

1. A method for determining whether a required length of weft is properly picked into a warp shed, comprising detecting a temporary rise in the warp tension caused by the weft upon beating.
 2. A weft detector adapted for use in a loom adapted to determine whether a required length of weft is properly picked into a warp shed, comprising a warp tension sensor for detecting a temporary rise in the tension of a warp array during beating, and means connected to said warp tension sensor for stopping the operation of said loom in the absence of said temporary rise in the warp tension.
 3. A weft detector according to claim 2, in which said warp tension sensor comprises two parallel-spaced guide members extending on a portion of said warp array transversely to the same and a sensiNg element positioned relative to and in contact said guide members to bias said portion of the warp array.
 4. A weft detector according to claim 3, in which said sensing element comprises a support arm having a flat surface which is in parallel with the plane of said warp array, a sensing member affixed to said surface of the support arm two elongated resilient members positioned on both sides of said sensing member, and a semi-cylindrical member disposed on said sensing member and said resilient members.
 5. A weft detector according to claim 4, in which said sensing member is of piezoelectric type.
 6. A weft detector according to claim 4, in which said sensing member is of magnetic type.
 7. A weft detector according to claim 4, in which said support arm is secured to a bracket which is adjustably mounted on a stationary rod for accommodation to different breadths of cloth.
 8. A weft detector according to claim 2, in which said means comprises a first pre-amplifier connected to said warp tension sensor for amplifying an electric signal corresponding to said temporary change in the warp tension, a first pulse generator for generating a single pulse at beating, a second pre-amplifier connected to said first pulse generator for amplifying said pulse signal, an AND circuit having its two inputs connected to the outputs of said first and second pre-amplifiers, a one-shot multivibrator connected to the output of said AND circuit, a second pulse generator for generating a single pulse in a predetermined time interval after the beating has taken place, a third pre-amplifier connected to said second pulse generator for amplifying said pulse signal, a NOT circuit connected to the output of said third pre-amplifier, a NOR circuit having its two inputs connected to the outputs of said one-shot multivibrator and said NOT circuit, a memory circuit connected to the output of said NOR circuit, a power amplifier connected to the output of said memory circuit, a relay connected to the output of said power amplifier, and a switch adapted to be actuated by said relay to open the power supply line leading to said loom in the absence of said temporary change in the warp tension. 